The present invention relates to hydraulic apparatus in general, and more particularly to a hydraulic control apparatus comprising a hydraulic master cylinder and a hydraulic slave cylinder for operating a mechanism remotely located from the master cylinder, the hydraulic control apparatus being prefilled with hydraulic fluid and pretested prior to shipment to a motor vehicle manufacturer, for example for installation in a motor vehicle. The present invention also relates to the method of prefilling the hydraulic apparatus with hydraulic fluid.
It is now known to prefill with hydraulic fluid a motor vehicle clutch control apparatus, comprising a master cylinder, a reservoir of hydraulic fluid, and a slave cylinder for operating the throwout bearing of a mechanical diaphragm spring clutch, as disclosed in U.S. Pat. Nos. 4,407,125 and 4,599,860, assigned to the same assignee as the present application. In addition, application Ser. No. 338,165, filed Jan. 8, 1982 and now abandoned, U.S. Pat. No. 4,624,290 and U.S. Pat. Nos. 4,585,106, 4,585,107, 4,585,108, 4,585,109 and 4,607,670 assigned to the same assignee as the present application, also disclose diverse forms of prefilled hydraulic control apparatus for motor vehicle clutches, and co-pending applications Ser. Nos. 555,666 and 555,668, both filed Nov. 28, 1983. disclose prefilled hydraulic control apparatus for transmission shifting mechanisms and throttle mechanisms, respectively.
Prefilling with hydraulic fluid and pretesting hydraulic apparatus for operating motor vehicle mechanisms such as mechanical clutches present the many advantages, for the motor vehicle manufacturer, of receiving a fully assembled mechanism comprising all the components filled with hydraulic fluid and pretested for proper operation, ready to install on a motor vehicle on the assembly line, without requiring that the components be installed separately, connected by way of a flexible conduit, and filled after installation with hydraulic fluid while being purged of any atmospheric air contained in the apparatus.
In apparatus wherein the slave cylinder, actuating the clutch release mechanism, takes the form of a conventional cylindrical cylinder-piston assembly with the piston rod projecting from the cylinder housing attached at its end to the clutch release lever, the slave cylinder being attached at some portion of the clutch bell housing, permanent connection of the master cylinder to the slave cylinder by means of a flexible conduit, and prefill of the apparatus with hydraulic fluid do not present much inconvenience, whether the slave cylinder or the master cylinder is installed first on the vehicle, and the other cylinder installed at some other subsequent station on the assembly line. The last installed component may be simply left dangling on the end of the flexible conduit, or may be attached by means of straps, wires or strings to some portion of the motor vehicle frame or body, until definitely mounted in its operative position. However, with the present trend towards utilizing annular slave cylinders, disposed concentric to the driveshaft and bolted either to the face of the transmission or gearbox casing or, in the alternative, mounted on or made integral with the clutch bell housing, such that the annular piston within the concentric annular slave cylinder may operate the clutch throwout bearing, it is difficult to provide a fully assembled, fully tested, prefilled apparatus, without some accompanying inconveniences. Such inconveniences relate to the requirement that the annular slave cylinder be installed first in the clutch bell housing, or on the transmission casing face, and the master cylinder on the end of the flexible line or conduit interconnecting the master and slave cylinders be provisionally attached, in some manner by strings, wires or straps to the motor vehicle frame, and subsequently installed in its proper position through the passenger compartment floorboard or bulkhead. The inventions disclosed in U.S. Pat. No. 4,624,290 and in U.S. Pat. No. 4,607,670 remedy the inconveniences enumerated hereinbefore with respect to preassembled prefilled hydraulic control apparatus for motor vehicle mechanical clutches, more particularly in structures wherein the throwout bearing is operated by a concentric annular slave cylinder, while presenting all the advantages of prefilled and pretested clutch control apparatus. Such results are achieved by a pretested prefilled hydraulic clutch control mechanism provided with an irreversible one-way quick-connect fitting or connector either at some point of the flexible conduit connecting the master cylinder to the slave cylinder, or at the end of the conduit connected to the master cylinder, or at the end of the conduit connected to the slave cylinder. The one-way quick-connect fitting or connector is arranged such that after the hydraulic control mechanism has been assembled, prefilled with hydraulic fluid and pretested, the connection between the master cylinder and the slave cylinder may be broken, without loss of fluid, or negligible loss of fluid, and the apparatus may be shipped to the motor vehicle manufacturer, completely filled with hydraulic fluid but in two separate portions such that the concentric slave cylinder may be made a part of the clutch bell housing, or of the transmission casing, and thus installed in the motor vehicle at whatever station on the assembly line that the clutch or transmission is installed, and such that the master cylinder may be installed in the motor vehicle also at whatever appropriate station, and the two connected together without any loss, or negligible loss, of fluid and without introduction of air into the apparatus.